Drum machines and sequencers have existed for many years. These devices play percussion and other sounds and samples in a rhythm pattern as controlled by a user. Typical output is an audio percussion track that can be played or recorded. New drum machines have been produced in software that run on general purpose computers, or in specialized sequence machines with input pads.
Many such drum machines provide a simple way to play beats, such as by striking an input pad or switch based on real-time, in that the user hits the pad just like a real drum in order to produce a sound. With other sequencers, a timeline is presented, allowing a user to indicate points on the timeline, so that when the sequencer is activated, the notes occur at according to the sequence on the timeline.
Modern devices such as personal digital assistants (PDAs), cell phones, music players have increased in memory and computer power and can run more powerful applications. Many of these devices have different types of inputs, including touch screens.
However, such touch screens are small and hard to present large amounts of information in a coherent, usable way. In the case of drum machines, presenting data varying from a single instrument beat to a complicated sequence with several sounds, and long sequences, is very difficult.